U.S. Pat. No. 3,079,505, issued to Weir, Van Valkenberg and Lippincott, discloses a high pressure optical cell that allows direct viewing or monitoring of radiation transmitted through a material that is compressed at pressures up to 160 kbar. Two cylinders, each with a central cone section removed and a small central aperture therein, are used to align and hold two small faceted diamonds, with the sample between the diamonds, and to transmit controllable axial force to the diamonds and to the sample. Removal of a conical section produces a central aperture through which radiation is directed. The two cylinders apply force over an annulus on each diamond, and the pressure transmitted to the sample is non-uniform. To the extent that the diamonds are characterized or iillustrated (FIG. 3A of Weir et al), they appear to be unbeveled.
Kirk, in U.S. Pat. No. 3,509,597, discloses an improvement of the Weir et al invention, wherein natural diamonds may be used for one or both of the anvil diamonds, and a thick transparent disc of plate glass in contact with the diamonds is used to transmit pressure to the diamonds. The Kirk invention appears to allow use of smaller size diamonds of lower quality for the diamond anvil, but the patent figures and text do not indicate use of any culet conf1guration other than an unbeveled one.
A diamond anvil high pressure cell, useful for producing observable pressures up to 700 kbar, is disclosed by Bell and Mao in U.S. Pat. No. 4,339,252. The inventors note that use of an apertured steel gasket with two opposed diamonds forming, in combination, the sample cell was disclosed by or for the inventors in an earlier report in 1978. The diamonds shown for illustration (FIGS. 2 and 3 of the Bell/Mao patent) have truncated culets with single bevels.